time for the auto-electrician matey? possibly the switch may be at fault (try swapping the one from the other car and see if it works?) and the interior light may be a seperate fault? otherwise it is probably a fault in the circuit (no power getting through) like a break in the wire somewhere or a connector block come undone?

Are the multi earth wires, ( 1 on the boot floor next to the fuel tank, 1 near the wing A stiffener under the bonnet) tight and clean? May be worth undoing them to clean. Other thing is, does it have a floor dipswitch? Check the wiring to that if so that they are not pulled out. Racking my brain cell here...

Nick wrote:Are the multi earth wires, ( 1 on the boot floor next to the fuel tank, 1 near the wing A stiffener under the bonnet) tight and clean? May be worth undoing them to clean. Other thing is, does it have a floor dipswitch? Check the wiring to that if so that they are not pulled out. Racking my brain cell here...

No floor dip switch Nick being a Mark 3. Will next check all the earth wires I can find!